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From: davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr)
Newsgroups: comp.sys.ibm.pc
Subject: Re: PC's serial port
Message-ID: <6223@steinmetz.steinmetz.UUCP>
Date: Wed, 10-Jun-87 15:05:08 EDT
Article-I.D.: steinmet.6223
Posted: Wed Jun 10 15:05:08 1987
Date-Received: Sat, 20-Jun-87 04:17:37 EDT
References: <2247@husc6.UUCP>
Reply-To: davidsen@kbsvax.steinmetz.UUCP (William E. Davidsen Jr)
Organization: General Electric CRD, Schenectady, NY
Lines: 23
Keywords: UART serial port baud rate transfer 8250

In article <2247@husc6.UUCP> chamoun@lownlab.harvard.edu (Nassib Chamoun) writes:
:
:On the 8088 PC the 8250 UART (serial port) uses a clock input of 1.8432 MHZ,
:when divided by 16 will yield to the maximum transfer rate of 115,200 bits per
:second.  Can someone tell me if the 8250 on 286 and 386 machines uses higher
:clock rates.  If so will it allow for faster transfer rates.  If not is
:there a way of transferring data at higher serial rates ?  any boards
:available ?  software or hardware gimmicks to alter 8250's input clock rate ?

As I recall, there is a field in one 8250 register which will allow you
to choose divide by 1, 16, or 64 (the last state is synchronous). You
could divide by 1, giving a max rate of 1.8432MHz, but I have no idea
what it buys you. Most of these parts don't like to run faster than
19.2kb.

NOTE: please don't send me your tale of how you run 115.2kb all the
time of 60 miles of abandoned railroad track... *most* 8250s don't run
reliably past 19.2kb, although you can probably go 76.8 with an error
correcting protocol and using 2 stop bits.
-- 
	bill davidsen		(wedu@ge-crd.arpa)
  {chinet | philabs | sesimo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me